A shift control device to be applied to a vehicle provided with an automatic transmission includes a detector and a shift mode control processor. The detector detects that the vehicle has passed through a tollgate through which the vehicle is able to pass without stopping. The shift mode control processor switches a shift mode of the vehicle from a first shift mode to a second shift mode the shift mode of the vehicle upon passing through the tollgate is the first shift mode and a predetermined condition regarding one or both of a speed of the vehicle and an accelerator opening degree of the vehicle is satisfied after the vehicle passes through the tollgate. In the first shift mode, a shift operation is performable by a driver, and in the second shift mode, a shift operation is performable by the automatic transmission.

A shift control device to be applied to a vehicle provided with an automatic transmission includes a detector and a shift mode control processor. The detector detects that the vehicle has passed through a tollgate through which the vehicle is able to pass without stopping. The shift mode control processor switches a shift mode of the vehicle from a first shift mode to a second shift mode the shift mode of the vehicle upon passing through the tollgate is the first shift mode and a predetermined condition regarding one or both of a speed of the vehicle and an accelerator opening degree of the vehicle is satisfied after the vehicle passes through the tollgate. In the first shift mode, a shift operation is performable by a driver, and in the second shift mode, a shift operation is performable by the automatic transmission.

A vehicle control system and a method for a vehicle running on a low friction road inhibit repetitive gear shifts of a transmission of the vehicle. The vehicle control system of the vehicle includes: one or more sensors for sensing an engine speed of the vehicle, an engine oil temperature, a position of an accelerator pedal, a lateral acceleration of the vehicle, a rotational angle of a steering wheel, or whether a low friction road running mode switch is turned on or off; and a controller for receiving sensor data from the sensors. In particular, the controller determines whether the vehicle satisfies an entry condition for performing a repetitive shift prevention control based on the sensor data, and controls a gear shift of the transmission and an engine torque to inhibit the repetitive gear shifts of the vehicle when the downshift occurs when the vehicle has satisfied the entry condition.

A vehicle control system and a method for a vehicle running on a low friction road inhibit repetitive gear shifts of a transmission of the vehicle. The vehicle control system of the vehicle includes: one or more sensors for sensing an engine speed of the vehicle, an engine oil temperature, a position of an accelerator pedal, a lateral acceleration of the vehicle, a rotational angle of a steering wheel, or whether a low friction road running mode switch is turned on or off; and a controller for receiving sensor data from the sensors. In particular, the controller determines whether the vehicle satisfies an entry condition for performing a repetitive shift prevention control based on the sensor data, and controls a gear shift of the transmission and an engine torque to inhibit the repetitive gear shifts of the vehicle when the downshift occurs when the vehicle has satisfied the entry condition.

A power transmission device is disclosed. The device includes a first rotating member, a second rotating member rotating relative to the first rotating member, and a torque transmission portion. The torque transmission portion is provided on the first rotating member and transmits torque from one of the first and second rotating members to the other via a hydraulic fluid. The torque transmission portion includes an oil chamber portion filled with the hydraulic fluid, a first piston pressing the second rotating member, a second piston retaining the hydraulic fluid in the oil chamber portion with the first piston, and an elastic portion elastically holding the second piston. The first piston receives pressure of the hydraulic fluid on a first pressure receiving area. The second piston receives pressure of the hydraulic fluid on a second pressure receiving area. The first pressure receiving area is smaller than the second pressure receiving area.

A power transmission device is disclosed. The device includes a first rotating member, a second rotating member rotating relative to the first rotating member, and a torque transmission portion. The torque transmission portion is provided on the first rotating member and transmits torque from one of the first and second rotating members to the other via a hydraulic fluid. The torque transmission portion includes an oil chamber portion filled with the hydraulic fluid, a first piston pressing the second rotating member, a second piston retaining the hydraulic fluid in the oil chamber portion with the first piston, and an elastic portion elastically holding the second piston. The first piston receives pressure of the hydraulic fluid on a first pressure receiving area. The second piston receives pressure of the hydraulic fluid on a second pressure receiving area. The first pressure receiving area is smaller than the second pressure receiving area.

A system and method for minimizing shift cycling for low speed engine operation with a vehicle cruise control. A vehicle control system operating in a cruise control mode determines a deficiency in vehicle speed between a measured vehicle speed and a cruise set speed. The deficiency is determined by comparing the vehicle speed to the cruise set speed, and includes using the compared value to find a cruise speed margin, which is continuously updated. While the cruise control system is active, the control system logic determines the time at which a transmission upshift occurs based on the cruise speed margin. The vehicle speed, at which the upshift is made, is determined as a function of the updated cruise speed margin. An upshift is not made, if a likely drop in vehicle speed would result in the event a downshift would occur once the upshift is made.

A system and method for minimizing shift cycling for low speed engine operation with a vehicle cruise control. A vehicle control system operating in a cruise control mode determines a deficiency in vehicle speed between a measured vehicle speed and a cruise set speed. The deficiency is determined by comparing the vehicle speed to the cruise set speed, and includes using the compared value to find a cruise speed margin, which is continuously updated. While the cruise control system is active, the control system logic determines the time at which a transmission upshift occurs based on the cruise speed margin. The vehicle speed, at which the upshift is made, is determined as a function of the updated cruise speed margin. An upshift is not made, if a likely drop in vehicle speed would result in the event a downshift would occur once the upshift is made.

A method of adjusting deceleration dependent shift points to maintain a target minimum turbine speed includes calculating a vehicle speed offset based on vehicle acceleration rate a predicted downshift delay for the target minimum turbine speed and converting the target minimum turbine speed to a target vehicle speed based on the deceleration condition. Thereafter, the method continues with determining a target gear based on the vehicle speed offset and the target vehicle speed, and downshifting to the target gear having vehicle speed less than or equal to a vehicle speed corresponding to the current turbine speed. The method ends with maintaining the target gear until a shift delay period is greater than a predetermined delay threshold.

An electronic control unit suppresses gear shifting more significantly in a second travel mode than in a first travel mode. Accordingly, frequent gear shifting of an automatic transmission in the second travel mode is suppressed, and superior ride quality is obtained. Meanwhile, an amount of a hysteresis in a gear shifting map is smaller in the second travel mode than in the first travel mode. Thus, duration of travel at an optimum gear stage is extended in the second travel mode, and fuel economy is improved. That is, in the second travel mode, drive power responsiveness to an acceleration and deceleration operation as in the first travel mode is unnecessary. Thus, even when gear shifting is suppressed, there is a low possibility that a driver feels a sense of discomfort.